1.
\(4cos^2x-4\sqrt{3}cosx+3=0\)
\(\Leftrightarrow\left(2cosx-\sqrt{3}\right)^2=0\)
\(\Leftrightarrow cosx=\dfrac{\sqrt{3}}{2}\)
\(\Leftrightarrow x=\pm\dfrac{\pi}{6}+k2\pi\)
2.
\(2sin^2x-7sinx+3=0\)
\(\Leftrightarrow\left(sinx-3\right)\left(2sinx-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}sinx=3\\sinx=\dfrac{1}{2}\end{matrix}\right.\)
Với \(sinx=3\Leftrightarrow\left[{}\begin{matrix}x=arcsin\left(3\right)+k2\pi\\x=\pi-arcsin\left(3\right)+k2\pi\end{matrix}\right.\)
Với \(sinx=\dfrac{1}{2}\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{6}+k2\pi\\x=\dfrac{5\pi}{6}+k2\pi\end{matrix}\right.\)
